1. Field of the Invention
The present invention relates to a traffic navigation apparatus installed on a vehicle for displaying routes from the current position of the vehicle to the destination thereof and a recommendable route from the current vehicle position to the destination on a displayed road map.
2. Description of the Prior Art
FIG. 34 shows the arrangement of a conventional traffic navigation apparatus disclosed in Japanese Patent Unexamined Publication No. 2-28800. In the figure, processor 1 consists of a CPU 11, a ROM 12, a RAM 13 and an input/output interface 14 connected together through a bus 15. A traffic information receiver 2 receives traffic information such as places of traffic congestion, road construction, traffic restriction and the like provided by a traffic information center using a quasi microwave system, a radiowave-guided system, or an FM multiplex communication system. A compact-disc player 3 reads out road map data from a CD-ROM which serves as a read-only memory.
A CRT display unit 4 displays map data read out of the CD-ROM and image signals produced by the processor 1 from traffic information received by the receiver 2. Indicated by 5 is an operation panel operated by a vehicle rider (driver or passenger), and 6 is a position sensor unit of an independent navigation type consisting of an azimuth sensor and a distance sensor. The processor 1 implements arithmetic processes for the signals provided by the position sensor unit 6 thereby to determine the current vehicle position.
Next, the operation of the above-mentioned conventional navigation apparatus will be explained on the flowchart of FIG. 35.
In step S1, the vehicle rider enters the start position, destination and condition of route selection through the operation panel 5. Then map information which complies with the input data is read out of the CD-ROM in the compact-disc player 3 and displayed on the CRT display 4. The processor 1 seeks a candidate route based on the specified route selecting condition (e.g., minimum distance or minimum time).
In step S2, it is tested whether or not a candidate route has already been entered. If no candidate route has yet entered, a candidate route is entered on the operation panel 5 in step S3. In step S4, routes other than the one entered in step S3 are sought by imposing another condition (e.g., within a certain distance from the entered candidate route).
In step S5, the most recommendable route among the routes sought in step S4 is selected based on the traffic information provided by the traffic information receiver 2, and the selected route is displayed on the CRT display unit 4 as shown by 30 in FIG. 36 (a). In step S7, it is tested whether or not the vehicle has reached the destination, and the process terminates on detecting the arrival.
If the vehicle has not yet reached the destination, the control sequence returns to step S1 to repeat the foregoing process, with the routine branching from step S2 to step S8 since the candidate route is already entered. In step S8, any change in traffic information or route selecting condition is tested. If no change is detected, the control sequence returns to step S1, or if any change is detected, the control sequence proceeds to step S5 to carry out a recurrent search, and a revised display is produced in step S6.
FIG. 36 (b) shows an example of the final display. The display includes marks of traffic congestion and a mark of traffic accident at a position 42 provided as a result of reception of traffic information by the traffic information receiver 2 and an altered route recommendation indicated by 40 from the current vehicle position 41 to the destination.
Although the conventional traffic navigation apparatus arranged as described above is capable of instructing a recommendable route which by-passes places of traffic congestion and accident based on traffic information received with the traffic information receiver 2, it does not consider places which the rider wants to avoid based on traffic information provided by other than the traffic information receiver 2 or based on the experience and preferance of the vehicle rider.